1. Field of the invention
The present invention relates to a knifing device for shredding straw or the like fibrous material. It also relates to a rotary knife assembly including a plurality of such a knifing device mounted in succession on a driving shaft.
2. Description of the prior art
A knifing device and assembly according to the invention serve in straw-shredding machines of which an example is disclosed in the Houle Canadian Pat. No. 1,037,839, issued on Sept. 5, 1978 (equivalent to U.S. Pat. No. 4,142,686 of Mar. 6, 1979). Machines of this type include a wheel-mounted base having a top wall pierced with parallel slots. Radial shredding knives spacedly mounted on a rotary shaft, located beneath the top wall, project across the slots to enter a rectangular straw-feeding rotary tube extending above the top wall and circumscribing the slots; the shaft and tube rotating about respective longitudinal axes normal to one another. The shredded straw is received into and is ejected by an elbowed conduit of which the upright curved end, secured to and beneath the top wall, surrounds the knives and slots and of which the horizontal end ejects the chopped straw from the machine to make beddings for animals in a barn or in a hen-house.
In the above mentioned Canadian and U.S. Houle patents, the radially projecting knives would appear to be unremovably secured to the shaft so that whenever one or a limited number of knives have to be sharpened or replaced, the complete shaft and knife assembly has to be removed from the machine which is a fairly complex operation considering the limited but frequent maintenance or replacement work that has to be done.
To avoid the above inconvenience, it has been suggested to removably mount each knife or shredding tooth, by bolts and nuts, on a receiving plate solid with and radially projecting from the rotary shaft so that the shredding teeth could be dismounted individually without having to remove the complete knive and shaft assembly. This idea is excellent and is an improvement over the Houle integral arrangement. However, the operation ca only be achieved by working through the very cramped space made available by the elbowed ejection conduit so that removing a tooth becomes a very different task and may also cause injuries to the hands.
Another solution that has been proposed consists in sliding the above mentioned mounting plates and teeth spacedly on the shaft; the latter having a cruciform cross-shape while the plates have a central cooperating cross-shape aperture to prevent relative rotation between the shaft and the plates. In this case, the shredding teeth are removably mounted on the plates by a limited number of elongated bolt rods each of which threads through suitable holes of both the plates and the teeth. The problem with this more adequate construction is that, as in the Houle device, the complete assembly has to be removed from the machine to reach one or a limited number of dull or broken knives. Also, once the assembly has been removed, it is usually necessary to slide a number of mounting plates and knives out of the shaft before reaching the one or ones that need be replaced or sharpened.
It is an object of the present invention to reduce appreciably the inconveniences mentioned above resulting from the necessity to remove one or a limited number of straw-shredding teeth from the mounting shaft for occasional replacement or sharpening.